MESA, Ariz.  Biologists are checking the diversity of fish in the Lower Salt River and reservoir lakes.

Among the 170 fish caught Monday in one drained section of the 80-foot-wide Arizona Canal -- and then returned to the water -- were whiskered channel catfish up to 3 feet long, colorful rainbow trout and Sonora suckers.

Most of the fish were largemouth bass, which are stocked in lakes for sport fishing.

State and federal biologists use the yearly canal draining to inspect an area just below the Granite Reef Dam on the Salt River Pima-Maricopa Indian Community between Mesa and Scottsdale.

Scientists examined the different species they found for a variety of reasons, including to ensure native fish are still flourishing.

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While two-thirds of native Arizona fish are considered endangered or imperiled, none of those are Salt River fish.

But changes in the habitats and the proliferation of nonnative species could threaten the future survival of native Salt River fish, said Paul Marsh, an ichthyologist and professor at Arizona State University.

"We have to figure out a balance," Marsh said. "There's a very clear conflict between sport fish and native fish, and it's not yet resolved."

Scientists also check on the canal section to find out whether Colorado River species from the Central Arizona Project canal downstream or vegetation-eating grass carp have managed to cross an electric barrier just west of the dam.

Wildlife managers want to make sure striped bass, which are aggressive predators, do not infiltrate the Salt River system.

If that happened, officials said native species in Saguaro, Roosevelt and other upstream lakes could be threatened and the bass might also replace common sport fish enjoyed by Arizona fishing enthusiasts.